Television



J. N. DYER TELEVISION May 25, 1943.

Original Filed'Feb. 24, 1941 INVENTOR JOHN /V. 075/? Y aha/41L,ATTORNEYS Patented May 25, 1943 TELEVISION John N. Dyer, Stamford,Conn., assignor to Columbia Broadcasting System, Inc., New York, N. Y.,a corporation of New York Original application February 24, 1941, SerialNo.

1942, Serial No. 446,385

Claims.

This invention'relates to television, especially to television in"natural colors. The invention particularly relates to apparatus of thetype employing rotating filter elements, and contemplates the provisionof a form of rotating element and arrangement of the rotating elementwith respect to a cooperating scanning device which will yield a compactassembly adapted to be conveniently housed in a cabinet, etc.

In color television systems in which the object field is scannedsuccessively in a plurality of colors and the signals transmitted to thereceiver for reproduction, the use of rotating disks have heretoforebeen suggested. Suitable disks having segments of novel design aredescribed in an application of Peter C. Goldmark. Serial No. 355.839,filed September '7, 1940, for "Color television. Such disks have beenfound to be quite satisfactory from the standpoint of operation.-

The use of rotating filter drums instead of disks has been suggested inan application of Peter C. Goldmark, Serial No. 370,008, filed December13, 1940, and entitled Television.

The present invention especially contemplates the combination of afilter drum, a mirror and a projection cathode-ray tube for theprojection of television images in color. The combination is arranged ina novel manner sothat the filter drum cuts ofi-a minimum amount oflight.

This application is a division of my applica-' tion Serial No. 380,097,filed February 24, 1941.

The invention will be more fully understood by reference to the specificembodiment illustrated in the drawing and the" following descriptionthereof. Inthe-drawing:

Fig. 1 is' an elevation of a specific embodiment in which a rotatingfilter drum is combinedwith a cathode-ray tube, mirror .andcorrectinglens for the projection of colorimages;"and

Figs. 2 and 3 are plan'andfront views,:re spectively, of the apparatusof Fig. 1. i j

Referring now to Figs. 1-3, a specific embodiment is illustrated whichisespecially applicable to the projection of images formed by acathoderay tube. A. cathode-ray receiver tube forming an image on theluminescent surface 2 thereof, is employed. This tube may be. of a typewhich produces a small but very brilliant image. Light from theprojector tube I is received by the concave mirror 3 and reflectedthrough the lens 4 to a suitably positioned screen 5. Lens 4 is designedto correct for the aberrations of the mirror 3. The mirror 3 and lens 4thus function in a manner similar to that of the so-called Divided andthis application June 9,

(c1. rad-5.4)

"Schmidt camera, familiar in connection with astronomical instruments.

A filter drum 8 is positioned with its peripheral surface closelyadjacent the scanning area 2 of the projector tube, and with at least aportion of its peripheral surface between the scanning area and themirror 3. Although the drum could be positioned to encircle theprojector tube I, in order to avoid impeding the light rays as much aspossible, the invention contemplates positioning the mirror and drum sothat the surface of the mirror extends within the drum.

As shown in Figs. 2 and 3, the filter drum impedes the rays of lightthrough only a relatively narrow vertical band. The drum is preferablypositioned so that the filters pass as closely as possible to the imageso that all rays of light which reach the mirror will pass through theproper filter. It will be apparent that if the central portion of themirror is reflecting, light rays therefrom will be reflected throughvarious parts ter segments will be absorbed and hence will not impairthe color reproduction. If the reflected rays impinge on a red filter,they will be partially attenuated and then allowed to pass. With a largenumber of filter segments this attenuation may'not be objectionable.However, if desired, suitable stationary masks may be placed insidethose portions of the drum lying between the mirror and the projectortube I, so as to cut oil rays which would otherwise pass through theperiphery of the drum.

The number of filter segments may be selected as desired, six groups ofthree red, green and blue filters being specifically illustrated.

The drum may be supported and driven by suitable bearings 1 as shown.Driving power may be supplied to pulley 8, or in any other desiredmanner. Or, a vertical central slice may be cut out of the mirror toallow the periphery of the drum to be attached to a central axle, andsupported and driven thereby. When such a slice is cut out, it will beunderstood that the surface of the mirror may still be considered topass within the drum.

The mirror and drum may be proportioned so that the mirror lies entirelywithin the drum in the vertical plane, or the mirror may extend somewhatbeyond the surface of the drum as shown in Fig. 1. In such case suitableslots 9 may be provided in the surface of th mirror.

In either case, those portions of the mirror which extend laterally fromthe drum (see Fig. 2) will receive light rays from the projector tubeand reflect them to the screen 5. If desired. the mirror may be widerthan it is high so as to provide mor light gathering power.

It will be understood that the present invention is not limited to themere details of construction and arrangement of the parts disclosed,since many modifications may be made by those skilled in the art withoutdeparting from the spirit and scope of the invention.

I claim:

1. In color television, in combination an electronic scanning devicecomprising an envelope having a two-dimensional scanning area associatedtherewith, a concave mirror positioned in th path of light of saidscanning area with its concave side toward the scanning area, and a arotatable color filter drum having a plurality of different color filtersegments on the pheripheral surface thereof, said drum being positionedso that its pheripheral surface moves adjacent said scanning area in thepath of light between said scanning area and said mirror.

2. In color television, in combination, an electronic scanning devicecomprising an envelope having a two-dimensional scanning area associatedtherewith, a concave mirror positioned in the path of light of saidscanning area with its concave side toward the scanning area, and arotatable color filter drum having a plurality of different color filtersegments on the pheripheral surface thereof, said drum being positionedwith its peripheral surface adjacent said scanning area in the path oflight between said scanning area and said mirror and the surface of saidmirror extending within said drum.

3. In color television, apparatus for projecting images in natural colorwhich comprises a cathode-ray tube having a luminescent surface at theend thereof on which two-dimensional images are successively reproducedin a plurality of side-by-side lines, means for projecting said imagesto a selected viewing screen comprising a concave mirror positioned inthe path of light from said images with the concave surface thereoftoward the luminescent surface, said luminescent surface beingsubstantially on the axis of said mirror, a rotatable substantiallycylindrical color filter drum having a plurality of different colorfilter segments arranged around the peripheral surface thereof, saiddrum being positioned so that its peripheral surface passes closely ad-Jacent said image surface. in the path of light from the images to themirror and the mirror being positioned so that the surface thereofextends within the drum, and means for rotating said drum to exhibitsaid images successively in diflerent colors.

4. In color television, apparatus for projecting images in natural colorwhich comprises a cathode-ray tube having a luminescent surface at theend thereof on which two-dimensional images are successively reproducedin a plurality of side-by-side lines, a concave mirror positioned in thepath of light from said images with the concave surface thereof towardthe luminescent surface, said luminescent surface being substantially onthe axis of said mirror, a correcting lens positioned in the path oflight of said mirror and adapted to correct aberrations thereof, saidmirror and correcting lens being adapted to project said images to aselected viewing screen, a rotatable substantially cylindrical colorfilter drum having a plurality of different color filter segmentsarranged around the peripheral surface thereof, said drum beingpositioned so that its peripheral surface passes closely adjacent saidimage surfac in the path of light from the images to the mirror and themirror being positloned so that the surface thereof extends within thedrum, and means for rotating said drum to exhibit said imagessuccessively in different colors.

5. Color television apparatus which comprises, in combination, anelectronic scanning device comprising an envelope having atwodimensional scanning area associated therewith, a concave mirrorpositioned in the path of light of said scanning area with its concaveside toward the scanning area, and a movable endless band hav ing aplurality of different color filter segments arranged therealong, saidendless band being positioned so that the color filter segments traversethe scanning area in the path of light between the scanning area andsaid mirror.

JOHN N. DYER.

